This invention relates to a ski boot toe binding of the type in which a boot toe holding member is swingably connected to a pivotable housing or body by a pair of arms.
The toe binding of this type is known in U.S. Pat. No. 3,709,510 to have a long critical restitution stroke which allows the toe holding member to automatically return to the normal toe holding central position without releasing the boot therefrom when the force applied to the toe holding member is released.
One of the most important functions of a ski boot toe binding is to absorb an instantaneously applied shock which is not great enough to cause the skier's leg to break, and to hold the ski boot to the binding, but which will release the ski boot rapidly when a severe shock is applied to the skier's leg for a relatively long time period. To achieve the above functions satisfactorily, it is said that a boot toe binding having high shock absorbing energy is desirable.
The shock absorbing energy of the toe binding is determined by functions of restorable lateral displacements and lateral forces applied to the toe holding member to displace the latter laterally, which forces will not displace the binding to a boot toe releasing position. It is said that the binding having a longer critical restitution stroke and a higher critical binding force has higher shock absorbing energy.
Namely, if the critical binding force of the binding is made constant, the binding having a longer critical restitution stroke has a higher shock absorbing energy. On the other hand, if the critical binding force of the binding is made greater beyond a certain value, the binding will not be released as desired and will cause the skier's leg to break. Therefore, the critical binding force of the bindings cannot be greater than a certain value in practice, and it is desired to provide a binding having longer critical restitution stroke.
However, if the toe binding having high shock absorbing energy with an elongated critical restitution stroke does not have a strong power of restitution, the binding will not be able to attain the desired function, and will be dangerous in skiing because it takes a relatively long time period before the toe holding member, slightly displaced by an unobjectionable shock, returns to the original toe holding position.
Thus, it is desired that the toe binding has not only a longer critical restitution stroke, but also strong power of restitution.
In the known toe binding set forth above, although it has a relatively long critical restitution stroke, there remains some room for improvements with respect to the power of restitution.
That is, in the known toe binding set forth above, a locking means, such as a locking pin engagable with a journal and a cam secured about the locking pin, functions to set, not only the pivotable housing or body, but also the toe holding member, in toe holding central positions under a spring force. The toe holding member is swingably connected to a pivotable housing by a pair of arms, and the cam in the locking means acts against the rear ends of the arms to urge the toe holding member to the central position thereof. Accordingly, when a lateral force is applied to the toe holding member when in the central position thereof, the pivotable housing receives such a force that tends to rotate the housing about the journal, whereby the locking pin engaging the journal is pressed against the journal. In the event that the lateral force applied to the toe holding member is severe enough to displace the toe binding toward the toe releasing position, the toe holding member is swung as the rear end of one of the arms acts against the cam to retract the latter against the spring force and then the locking pin is disengaged from the journal, thereby rotating the pivotable housing about the journal to release the boot toe. However, while the locking pin is being disengaged from the journal, a high frictional resistance is produced therebetween by the force tending to rotate the pivotable housing about the journal.
Such a high frictional resistance is also produced when the toe holding member is displaced to a certain degree not reaching to the toe releasing position returns to the original toe holding central position by the decrease or elimination of the lateral shock applied to the boot toe.
Accordingly, in such a known toe binding set forth above, the power of restitution of the binding is greatly reduced due to high frictional resistance. On the other hand, if the spring force of the binding is made stronger to increase the power of restitution of the binding, due to the frictional resistance between the locking pin and the journal, the binding force of the binding will be much increased so that it will not release the toe as desired and, therefore, the spring force of the binding cannot be increased beyond a certain relatively low value.
Although the binding set forth above has a relatively high shock absorbing energy, the binding will not be satisfactory for practical use due to the low power of restitution.